Closure with improved pull tab

Abstract

This relates to the construction of a pull tab integrally formed on a closure which is bonded to a container by way of a rupturable bond. Instead of utilizing the conventional pull tab which is normally integrally connected to the closure, the pull tab has been modified so as to provide two or more lines of bond rupturing forces as opposed to the prior art original single line with the two or more lines of bond rupturing forces having a tendency to spread in opposite directions and thereby greatly reducing the force required to initiate a rupture of the bond between the closure and the container. Numerous different types of notches, openings and the like are provided to provide for the separate lines of bond rupturing forces. These notches, openings and the like also function to constrain stray electric current induced into an intermediate metal layer of the closure and pull tab flowing into the pull tab, thereby reducing the power requirement for heating the closure to a bonding temperature. Employing selective geometries of the notches, openings and the like creates selective geometries of the bond to achieve ease of initiating rupture.

I claim: 
     
       1. A closure having opening means in the form of a pull tab projecting therefrom, said closure being of the type adapted to have a rupturable bond with a container with such bond extending generally transversely of said pull tab in two opposite directions, said closure during application to said container having said pull tab projecting radially outwardly therefrom, said closure being improved by having at least one void adjacent such bond defining current density focus means and force directing means for dividing the force exerted by said pull tab on said closure during closure removal in two or more paths to facilitate initial bond rupture. 
     
     
       2. A closure according to claim 1 wherein said pull tab is an integral extension of said closure. 
     
     
       3. A closure according to claim 1 wherein said pull tab is an integral extension of said closure joined to said closure by a neck portion, and said current density focus means and force diverting means is in said neck portion. 
     
     
       4. A closure according to claim 3 wherein said force directing means is in the form of a force dividing opening in said neck portion. 
     
     
       5. A closure according to claim 4 wherein said force dividing opening is generally circular. 
     
     
       6. A closure according to claim 4 wherein said force dividing opening is elongated axially of said pull tab. 
     
     
       7. A closure according to claim 4 wherein said pull tab is of the ring type including a finger receiving opening, and said force dividing opening extends from said finger receiving opening into said neck portion into two side-by-side parts. 
     
     
       8. A closure according to claim 7 wherein said force dividing opening is in the form of an elongated notch. 
     
     
       9. A closure according to claim 7 wherein said force dividing opening is in the form of an elongated notch of a generally V-shape having a wide end at said finger receiving opening. 
     
     
       10. A closure according to claim 9 wherein said notch extends through said neck portion into said closure per se. 
     
     
       11. A closure according to claim 1 wherein said pull tab is an integral extension of said closure and is joined to said closure along a juncture line forming a continuation of the periphery of said closure, and said force diverting means is in the form of an opening in said pull tab adjacent said juncture line. 
     
     
       12. A closure according to claim 11 wherein there are a plurality of neck openings. 
     
     
       13. A closure according to claim 12 wherein said openings are arranged in an arched shaped pattern facing away from said closure. 
     
     
       14. A closure according to claim 12 wherein said openings are arranged in a generally straight line pattern. 
     
     
       15. A closure according to claim 9 wherein said notch is relatively wide and has a generally rounded bottom. 
     
     
       16. A closure according to claim 8 wherein said notch is generally rectangular. 
     
     
       17. A closure according to claim 3 wherein said said force directing means is in the form of a force dividing slit in said neck portion. 
     
     
       18. A closure according to claim 3 wherein said closure including said pull tab includes a metal layer into which electrical current is introduced to heat a limited area of said closure to bond said closure to a container, and said force directing means includes means interrupting said metal layer in said pull tab to create a desired current flow path in said pull tab. 
     
     
       19. A closure having opening means in the form of a pull tab, said pull tab during application to a container projecting radially outwardly therefrom and connected thereto by a neck portion, said closure being of a laminated constructure including a metal layer into which electric current is to be induced to heat said closure to heat bond said closure to a container, the metal layer in said pull tab having an undesired influence on the flow of electrical current and normally requiring more electrical current input to properly heat said closure in the area of said pull tab, said closure being improved by having electric current flow directing void means in said pull tab neck portion for controlling stray induced electric current flow in said pull tab and thereby reducing the overall induced electric current required to heat said closure to a bonding temperature. 
     
     
       20. A method of reducing the power required to induction heat and bond a closure to container comprising the steps of providing a container and a closure having opposed heat bondable surfaces with the closure having a pull tab connected thereto and projecting radially outwardly therefrom during application to a container by a neck portion for later effecting peeling of the closure from the container and the closure including the pull tab being of a laminated construction including an intermediate metal layer into which electric current is to be induced, and providing the pull tab neck portion with electric current flow directing void means for controlling stray induced current flow in said pull tab.